FRUITS AND SEEDS
advertisement
FRUITS AND SEEDS Fruits Part of sexual reproduction unique to angiosperms Develops from fertilized ovary Protect the enclosed seeds and aids in seed dispersal Widely utilized as a significant food source Fruit wall or Pericarp Develops from the ovary wall Composed of three layers outer exocarp middle mesocarp inner endocarp Appearance of these three layers varies among different fruit types Fruit Types I: Simple Fruits Derived from the ovary of a single carpel or several fused carpels Can be fleshy or dry Type I.a: Simple fleshy fruit Derived from the ovary of a single carpel or several fused carpels Often soft and juicy Seed dispersal occurs when an animal eats the fruit Types of simple fleshy fruits BERRY DRUPE -HESPERIDIUM -POME -PEPO Berry Thin exocarp Soft fleshy mesocarp Endocarp with one to many seeds Tomatoes, grapes and dates Hesperidium Berry with a tough leathery rind Oranges, lemons, and other citrus fruitS Pepo Tough outer rind that has both receptacle tissue and exocarp Mesocarp and endocarp are fleshy All members of the squash family (pumpkins, melons, and cucumbers) Drupe Thin exocarp Fleshy mesocarp Hard stony endocarp which encases the seed Cherries, peaches, and plums Exocarp Mesocarp Endocarp Pome Fleshy part develops from the enlarged base of the perianth (calyx and corolla) that is fused to the ovary wall Apples and pears Accessory fruits Contain flower parts other than the ovary Both the pepo and pome are example Type I.b: Simple dry fruits Derived from the ovary of a single carpel or several fused carpels Pericarp may be tough and woody or thin and papery Two types: dehiscent indehiscent Dry dehiscent fruits Split open at maturity to release seeds Wind often aids seed dispersal Types characterized by how they open: * Follicle - splits open along one seam (magnolia and milkweed) * Legume - splits open along two seams (beans and peas) * Capsule - several pores or slits (cotton and poppy) Legume - pea Legume pod splits along two seams to disperse seeds Capsule Cotton fruit is a capsule splitting open along five lines Seeds are covered with long hairs (trichomes) which are the commercial cotton fiber Indehiscent fruits Do not split open to release seeds Common types Achene Samara Grain Nut ACHENES SAMARAS One-seeded fruit Pericarp free from the seed Sunflower “seeds” Winged achenes Dispersed by wind Fruit in maple trees and ash trees Grains Also called caryopsis Single seeded fruits Pericarp fused to seed coat Fruits of all cereal grasses: wheat, rice, corn and barley Wheat grain Fused seed coat and ovary wall layers Nuts One-seeded fruits Hard stony pericarps Hazelnuts, chestnuts, and acorns Other things commonly called nuts that are not true nuts but are actually seeds Fruit Types II: Aggregate fruits Develop from a single flower with many separate carpels Raspberries and blackberries Strawberries also contain accessory tissue Seeds on the surface are actually separate achenes inserted on the enlarged, fleshy, red receptacle Raspberries and Blackberries Aggregate-Accessory Fruit Strawberries also contain accessory tissue Seeds on the surface are actually separate achenes on enlarged, fleshy receptacle Fruit Types III: Multiple fruits Result from the fusion of ovaries from many separate flowers on an inflorescence Figs and pineapples are examples of multiple fruits one of many ovaries that are fused together Seed Structure and Germination Seeds Develop from the fertilized ovules Include an embryonic plant and some form of nutritive tissue within a seed coat Because of the stored nutrients many seeds are valuable foods Dicots and monocots Refers to the number of seed leaves or cotyledons present in the seed Dicot seeds have two cotyledons Monocots have one cotyledons Dicot seed Cotyledons attached to and enclose the embryonic plant Cotyledons occupy the greatest part of the seed Cotyledons have absorbed the nutrients from the endosperm which may be entirely used up Dicot seed - Lima bean Thin seed coat Hilum and micropyle visible on surface * Hilum - attachment * Micropyle - opening in the integuments If the seed coat is removed the two large food-storing cotyledons are visible Dicot embryo Consists of : Epicotyl - part that develops into the shoot; typically has embryonic leaves - also called a plumule Hypocotyl - portion of embryo between cotyledon attachment and radicle (between stem and root) Radicle - the embryonic root Monocot seed Cotyledon transfers food from the endosperm to the embryo In several monocot families large amounts of endosperm are present Monocot seeds - Corn kernel Reminder: a grain is a one-seeded fruit in which the seed coat is fused to the pericarp Extensive endosperm occupies much of the seed Small embryo with a single cotyledon Presence of a coleoptile and the coleorhiza Seed germination Absorption of water Emergence of the radicle Shoot emerges: In dicots the hypocotyl elongates and breaks through the soil In monocots the coleoptile emerges protecting the epicotyl tip Soon after the tissues are exposed to sunlight, they develop chlorophyll and begin to photosynthesize Tomatoes Native to Andes Mts in South America First cultivated in Mexico Spanish Conquistadors introduced tomatoes to Europe in the 16th century What is in a name? Name among native peoples in Mexico was tomatl In Europe there were lots of names for this fruit - love apple or pomme d’amour was the French name Scientific name Lycopersicum esculentum (meaning edible wolf peach) Poisonous Relatives Member of the family Solanaceae (called the potato or tomato family) Family known for its poisonous plants Also called the nightshade family because of deadly nightshade and henbane Also called tobacco family Suspect Plant Because of the poisonous relatives, tomatoes were suspected by many as poisonous Hard reputation to live down In 1820 Col. Robert Johnson ate a bushel of tomatoes in front of a crowd to prove they were safe Popular “vegetable” Although botanically it is simple fleshy fruit (a berry), in 1893 the Supreme Court ruled it was a vegetable Widely used in fresh, canned, dried, pickled, and processed varieties Also a favorite experimental tool - used in space shuttle, genetic engineering, and cloning experiments Apples - Malus pumila Family Rosaceae Long history of use One of the first trees cultivated Native to Caucasus Mts of western Asia Many legends associated with apples Apple Varieties Pome - simple accessory fruit Hundreds of varieties exist but only a few dominate the market Delicious, Rome, Gala, McIntosh Most apple trees are produced by grafting rather than by seeds Grafting creates thousands of identical copies with the desired traits Citrus Fruits Citrus Fruits - Oranges Members of the family Rutaceae Fruit is a hesperidium Rind impregnated with oil glands (oils important for perfumes and cosmetics) Individual carpels filled with one-celled juice sacs Fruits high in Vitamin C Citrus Fruits Most citrus are native to southeast Asia Citrons first citrus fruit introduced to Mediterranean countries during Greek and Roman times Sweet oranges not introduced till 16th century Introduction to New World Spanish and Portuguese explorers introduced citrus to New World Sour oranges grown in Florida by 1565 Sweet oranges introduced after 1821 grafted onto sour orange rootstock Florida remains leading orange-producing state for juices Grapefruit developed in Caribbean (pummelo x orange) Pummelos Navel Orange Seedless orange - propagated asexually First developed in Brazil by an American missionary in 19th century Two seedlings introduced to California in 1873 - believed that all navel oranges today are descendants of these two trees Chestnuts - Castanea dentata Member of the Fagaceae - Oak Family Nuts have a long history of use Nuts produced in groups of 3 surrounded by spiny burr (actually bracts) Spiny bracts Individual nuts Chestnuts American chestnut tree was once one of the most abundant trees in North American forests Wood widely used for furniture, shingles, poles, ships masts Chestnut Blight Fungal disease first reported in 1904 in New York Spread throughout range from Atlantic Coast to Mississippi River Estimated 1 billion chestnut trees died Chestnuts can resprout from roots but eventually will succumb to disease Research on blight resistant trees Durian Fruit native to southeast Asia, Malaysia, Thailand, Indonesia Called “King of Fruits” Durians Large fruits - 10-15 lbs Often collected from wild although cultivation is spreading Not available outside of Asia Custard-like pulp that is said to be heavenly Durians Said to be the most delicious fruit on Earth and the worst smelling Sold in open markets but prohibited in many cities “No durians allowed”
